1- 550-600 hp is in your dream !! Sorry
2- your engine , is a JDM WRX 1993 or 1997 !!! STI have all red intake !!
S
3- WRX JDM have around 260 hp and STI 280 hp !! No more !
I modify Subaru all day long , and I never saw 500 hp whitout put over 25 000$
Good luck
WRX engine 1993-97
STI engine 1993-97
1998-2000 WRX or STI ( Intercooler is straight )